View Full Version : Old school Trane Varitrac Problem
01-30-2007, 09:14 AM
I have a Varitrac II on a Trane Ych600. 1996 Installed. I find the unit down every morning. Under unit summary I read fan failure. I reset it and it runs all day. I have disconnected the time clock and it runs occupied and never shuts down. It only shuts down overnight possibly when controlling unocc heat setpoints. I have simulated occ & unocc operation without failure. But over night it fails. I am sensing static pressure. 2h2c . My bypass works.
01-30-2007, 09:13 PM
I assume you are doing direct communications with the unit & panel. The fan failure should be in the unit, not the VariTrac Panel. The rooftop is sending the alarm to the panel.
It should be a DP pressure switch for the fan status input. I would check that and adjust/replace if necessary.
Since it appears to only be happening during unoccupied times with low building loads, I would also check the fan status switch with the by-pass open 100%. It could be when the by-pass is open 100% and circulating directly back into the unit, the DP drops very low across the fan and the switch opens.
01-30-2007, 09:17 PM
CCP is failing the fan at calibration time.
02-02-2007, 02:54 PM
Thanks for the response. I found out it was an airflow problem in unocc. It was causing the pressure switch to signal fan failure.
02-04-2007, 07:44 PM
What was the airflow problem?
02-26-2007, 04:17 PM
The exact problem as Balibe described was happening. One zone calling unoccupied would always cause the problem. Too much rooftop to try and feed one area. I increased my static setpoint and my problem went away. I do have some more air noise. But that is what you get with large roof tops with VVT. When people turn down the minimum air setpoints the bypass becomes undersized. I am forcing more air down the duct now and it stays running. not the best situation but it is running.
how many zones on this system?
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